1 1/2 cup cake flour, spooned and leveled in cup
1 1/2 tsp baking powder
1/2 tsp salt
1/2 cup unsalted butter, softened
1 1/2 cup granulated sugar
1 large egg
2 large egg whites
2 1/2 tsp vanilla extract
1/2 tsp vanilla bean paste
1/2 C milk
1/4 C buttermilk
Spray 2 9 inch pans or line cupcake pan with liners.
Preheat oven to 350 degrees. Sift cake flour into a mixing bowl. Add baking powder and salt and whisk dry mixture, 20 seconds, set aside.
In the bowl of an electric stand mixer, whip together butter and granulated sugar until pale and fluffy. Mix in egg, then mix in egg whites one at a time, blending until combined after each addition. Mix in vanillas. Working in three separate batches, beginning and ending with flour mixture, add 1/3 of the flour mixture, alternating with 1/2 of the milks and mixing just until combined after each addition. Using a rubber spatula, gently fold in sprinkles.
Divide mixture, 2-3 tbsp, into muffin cups. Alternatively, evenly distribute batter into two cake pans. Bake in preheated oven 17 – 19 minutes for cupcakes or 20-28 minutes for cake layers until toothpick inserted into center of cupcake comes out clean. Allow to cool